The present invention relates in general to integrated circuits and in particular to an output driver or buffer circuit with current-controlled output rise and fall times.
In certain applications, an electronic system may require an integrated circuit (IC) to drive other circuitry that present variable load conditions. Output driver circuits have been designed that provide variable drive capability. One known approach, for example, is to switch in or out one or more output transistors in parallel to vary the current drive of the output buffer. This technique, however, usually requires more transistors with various sizes than the minimum size may require, which is costly. Further, connecting more transistors to the output node by itself often results in varying the output load. This approach is also sensitive to timing constraints.
There is a need for an output driver circuit that can provide variable drive capability while maintaining accurate control over rise and fall times of the output signal.